Intercommunicating system



Aug 5, 1947 R. H. HERRlcK INTERCOMMUNICATING SYSTEM Filed April 2e, '1945 rllll INVENTOR. ROSWELL H. HERRICK ATToRyEY Patented Aug. 5, V1947 IN TERCOMIVIUNICATING SYSTEM Roswell H. Herrick, Chicago, Ill., assigner to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application April 26, 1945, Serial No. 590,472

7 Claims. 1

The present invention relates to telephone systems and more particularly to improvements in intercommunicating telephone and signaling systems of the type in which a loudspeaker is employed at one station and the usual telephone instrument is employed at another station.

The present invention is an improvement on my prior Patent No. 2,345,046, which was granted March 28, 1944, wherein an intercommunicating system of the character described is arranged in an improved manner to minimize all signal energy losses in the signal transmission channels and to minimize the number of line conductors used to interconnect the stations.

It is an object of the present invention to provide an improved system of the character described in which loudspeaking telephone sets are employed at two stations and the usual telephone sets are employed at one or more other stations, in which means are provided at each of said other stations for selectively associating them with either one of the loudspeaking stations, and in which signal devices for producing sounds of different character are arranged to be operated from the loudspeaking telephone sets to identify the origin of calls initiated therefrom.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be under stood by reference to the specilication taken in connection with the accompanying drawing which illustrates an improved intercommunicating system characterized by the features briefly referred to above.

Referring now to the drawing, the intercommunicating system there illustrated comprises two loudspeaking telephone sets, a battery box, two signal devices, and one or more of the usual telephone sets of which only one is shown. The system is intended primarily for residential use. The two loudspeaking telephone sets may be located at the front and rear doors of a residence and one or more ordinary telephone sets may be located within the residence. Alternatively, the system may be used to provide communication facilities between several oices and a reception room which is common to the several oices.

Briefly considered, the equipment provided at each loudspeaking station comprises a transmitter I, a loudspeaker 2, two condensers 3 and 4, two coupling transformers 5 and 6, a resistor l, and a non-locking key 8. Each of the interior stations comprises a handset including a transmitter 9 and a receiver I0, a hook or cradle switch II, and a non-locking key I2. The battery box,

which contains apparatus common to all of the stations, comprises a transformer I3, a battery I4, a condenser I5, and two relays A and B. Separate channels are used for transmission and reception of voice signals at each station. More specifically, conductors 2I and 22 define a channel for the reception of voice currents at the front door station, and conductors 22 and 23 define a second channel for the transmission of voice currents by the front door station. Conductor 2l is also used in conjunction with conductor Zbl to providea circuit for controlling signal device 25 from the front door station. Similarly, conductor 2| is used in conjunction with conductor 2.4' to provide a circuit for controlling signal device 26 from the rear door station. Conductors 3| and 32 deiine a channel for the transmission of voice currents by the interior station, and conductors 32 and 33 deiine a second channel for the reception of voice currents at the interior station. Conductor 32 is also used in conjunction with conductor 34 to provide a circuit for controlling relay A from the interior station.

In considering the operation of the system it will rst be assumed that a caller appears at the front door and operates key 8, which may replace the usual door bell push button. A circuit will then be closed from the positive terminal of battery Ill, through the left winding of transformer I3, through contacts AI, over lead ZI, through contacts of key 8, over conductor 24, through bell 25, and over conductor 21 to the negative terminal of battery I4. When a party within the residence hears the bell he will remove the handset of the nearest interior station, which will be assumed to be the one illustrated, from its support. A circuit is thereupon completed for energizing transmitter 9 from the negative terminal of battery I4, through the right winding of transformer I 3 and relay B, over conductor 3l, through the upper contacts of switch I I, transmitter 9, and back to the positive terminal of battery I4 over lead 32. Coincident with the closure of this circuit the lower contacts of the hook or cradle switch II are closed to bridge the receiver I il across conductors 32 and 33. Relay B, being energized in series with transmitter 9, operates and at its contacts BI disconnects conductor ZI from transformer I3, and at its contacts B2 completes a circuit for energizing the transmitter I at the front door station. The latter circuit may be traced from the positive terminal of battery I4, through contacts B2 and A2, over conductor 22, through the left winding of transformer 6, transmitter I, resistor l, over conductor 24, through bell 25, and over conductor 21 to the negative terminal of battery I4. The resistance of this circuit is high enough so that the bell will not operate in series therewith. The party at the interior station speaks into transmitter 9 in answer to the call. The varying resistance of transmitter 9 causes an undulating current to flow over the previously traced energizing circuit for the transmitter thus causing a corresponding alternating voltage to be induced in the left Winding of transformer I3, which voltage is impressed on the primary Winding of transformer over conductors 2| and 22 through contacts B2 and A2 and in series with condenser 4. The resulting alternating current flowing in the primary winding of transformer 5 causes a corresponding alternating voltage to be induced in the secondary winding, which voltage is impressed on loudspeaker 2 for aural reproduction. The condenser I6 shunted across the winding of relay B provides a low impedance path for the undulating voice currents produced by operation of transmitter 9. The caller may now converse with the party at the interior station by speaking into transmitter I. An undulating current will then How through the left winding of transformer 6, due to the varying resistance of transmitter I, and will induce a corresponding alternating voltage in the right winding. Condenser 3 increases the magnitude of the current undulations, for a given change in the resistance of transmitter I, by tending to maintain the total voltage across transmitter I and the primary winding of transformer 6 constant. The alternating voltage induced in the secondary winding of transformer 6 is impressed on receiver I6 for aural reproduction over conductors 22 and 23 and conductors 32 and 33. When the conversation is completed and the handset of the interior telephone set is restored on the cradle or hook switch II the circuit for energizing transmitter 9 in series with relay B is interrupted. Relay B restores and opens the energizing circuit for transmitter I at contacts B2.

If the caller had appeared at the rear door in place of at the front door switch 8 would have been operated. In this case a circuit is completed to buzzer 26 from the positive terminal of battery I4, through the left winding of transformer I3 and contacts BI, over conductor 2 I through contacts of key 8', over conductor 24', through buzzer 26, and over conductor 2l to the negative battery terminal. When the party within the residence hears the buzzer he lifts the handset of the nearest interior telephone set and momentarily operates key I2, or the corresponding key at an interior station not shown. A circuit is completed to relay B in series with transmitter 9 by the closure of the hook or cradle switch contacts as previously described. Relay B operates. When key I2 is operated a circuit is completed to relay A from the positive terminal of battery I4, over lead 32, through contacts of key I2, over lead 34, and through relay A to the negative terminal of battery I4. Relay A operates, transfers the left winding of transformer I3 from conductor 2I to conductor 2|' at contacts AI, transfers the armature of contacts B2 from conductor 22 to conductor 22 and closes its locking circuit through contacts B2 at contacts A2, and transfers conductor 33 from conductor 23 to conductor 23' at contacts A3. Transmitter I' is energized from the positive terminal of battery I4, through contacts B2 and A2, over lead 22', through the left winding of transformer 6', transmitter I', resistor l', over lead 24', through buzzer 26, and over conductor 2'I to the negative terminal of battery I4. The resistance of this circuit is high enough so that buzzer 26 will not operate in series therewith. Conversation may now proceed between the party at the rear door and the party within over circuits similar to those previously described. The corresponding parts of the front and rear door stations have the same reference characters excepting that primes are used for the rear door station. When the handset of the interior telephone is replaced on its support, the circuit for energizing transmitter Sl in series with relay B isl opened. Relay B consequently restores, opens the circuit for energizing transmitter I', and opens the locking circuit for relay A at contacts B2. Relay A restores.

When the intercommunicating system is used as just described there is no necessity for initiating a call from the interior station. However, as previously mentioned, the system may be employed to provide communication between several offices and a common reception room. In such a case one of the loudspeaking telephone sets would be located in each ofce and the ordinary telephone set would be located on the receptionists desk. One office may be called from the ordinary telephone set, or the interior station illustrated, by simply lifting the handset and speaking into the transmitter. To call the second office the key I2 is operated momentarily after lifting the handset causing relay A to operate and associate the transmitter and loudspeaker of the second office with the receptionists telephone set.

Since the signal current transmission channels described above do not include amplifiers, the greatest possible efficiency is required to obtain an adequate loudspeaker Volume from the signal currents produced by the transmitters provided at the interior stations, and also to obtain adequate handset receiver volume from the front or rear door transmitter I when it is required that this transmitter should respond to sound waves originating at points two or three feet removed therefrom. To obtain the required volume of reproduction at both the loudspeaking stations and the interior stations the impedances between the various connected elements are carefully matched and the line losses are held to a minimum.

While a particular embodiment of the invention has been described, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

1. In an intercommunicating system, a plurality of first stations and a second station each including telephone instruments, a plurality of audible signal devices for producing sounds of different character, each 0f said signal devices corresponding to one of said rst stations, a switch at each of said first stations for operating the corresponding one of said audible signal devices, the telephone instruments at said second station being normally associated with the telephone instruments at one of said rst stations in response to the answer of a call, means controlled by said second station for disassociating the telephone instruments thereat from the telephone instruments at said one rst station and for associating them with the telephone instruments of another of said rst stations to establish two way communication therebetween, said audible signal devices serving to indicate the origin of a call initiated by any of said first stations,

2. In an intercommunicating system, a plurality of rst stations each including telephone instruments, a plurality of further stations each including telephone instruments, a plurality of audible signal devices for producing sounds of diiferent character, each of said signal devices corresponding to one of said first stations, a switch at each of said rst stations for operating the corresponding one of said audible signal flevices, the telephone instruments at said further stations being normally associated with the telephone instruments at one of said first stations in response to the answer of a call, means controlled by any of said second stations for disassociating the telephone instruments thereat from the telephone instruments at said one first station and for associating them with the telephone instruments of another of said first stations to establish two way communication therebetween, said audible signal devices serving to indicate the origin of a call initiated by any of said first stations.

3. In an intercommunicating system, a pair of first stations and a second station each including telephone instruments, a pair of audible signal devices for producing sounds of diierent character, each of said signal devices corresponding to one of said first stations, a switch at each of said rst stations for operating the corresponding one of said audible signal devices, interstation circuits normally coupling the telephone instruments of one of said first stations to the telephone instruments of said second station when a call is answered thereat, means controlled by said second station for altering said interstation circuits so as to couple the telephone instruments of the other of said first stations to the telephone instruments of said second station, said audible signals serving to indicate the origin of a call initiated by either of said first stations.

4. In a telephone system for use between several entrances and the interior of a residence, transmitting and receiving units located at each of two entrances and within the residence, a four conductor line extending from each entrance to a switching point within the residence, a pair of audible signaling devices each connected in series with a first one of the conductors of each of said lines, a switch at each entrance for connecting said first conductors to one of the other three conductors of said lines to operate the corresponding signaling device, the other three conductors of each of said lines defining a pair of oppositely directed one-way talking circuits between the transmitting-and receiving units at the entrances and the transmitting and receiving units within the residence, means at said switching point for selectively associating the transmitting and receiving units within the residence with either of said lines, said audible signal devices each producing a different sound in order to identify a calling entrance.

5. A telephone system as claimed in claim 4 in which said first conductor and another one of the other three conductors of each of said lines dene normally open circuits for energizing the transmitting units at said entrances, and means responsive to an answer of a call initiated from either of said entrances for completing one of said circuits.

6. In a telephone system for use between several entrances and the interior of a residence, transmitting and receiving units located at each of two entrances and at a station within the residence, a line extending from each entrance to a switching point within the residence, a pair of audible signal devices each arranged to be controlled over a corresponding one of said lines, the transmitting and receiving units of the interior station being normally associated with the transmitting and receiving units at one of the entrances over one of said lines in response to the answer of a call, and means at said switching point controlled from the interior station for disassociating the transmitting and receiving units thereat from said one line and for associating them with the transmitting and receiving units at the other of the entrances over the other of said lines, said audible signal devices each producing a different sound in order to identify a calling entrance.

'7. In a telephone system for use between several entrances and the interior of a residence, a telephone instrument located at each of two entrances and at a station within the residence, lines extending from each entrance to the interior station, a pair of signal devices each arranged to be operated from one of the entrances over a corresponding one of said lines, the telephone instrument at the interior station being normally associated with the telephone instrument at one of said entrances in response to the answer of a call, said signal devices serving to identify a calling entrance, and means at the interior station operative to cause the telephone instrument thereat to fbe disassociated from the telephone instrument at said one entrance and to be associated With the telephone instrument at the other of said entrances.

ROSWELL H. HERRICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 559,087 Smith Apr. 28, 1896 2,346,548 Atkins Apr, 11, 1944 

